Power lawn mowers of the horizontal rotary blade type are operated by users of differing age, prudence, and mechanical aptitude. The mowers are used on lawns of various configurations and elevations. Occasionally, such users lose control of the mower by inattention, loss of balance, or poor footing. Under such circumstances, it is possible for the mower to roll by its inertia or due to lawn elevation in such a manner as to injure the user. Further, through inattentiveness or lack of common sense, users have been known to insert hands and feed within the housing containing the rotating blade. The U.S. Government, through a study, has recognized such users should either be protected from themselves or the inherent dangers of operating such mowers and has, accordingly, mandated the need for a lawn mower clutch brake assembly on all horizontal rotary blade type mowers. In view of this mandate and the need for a clutch brake assembly which will meet U.S. Government standards, applicant has conceived of the following invention.